Ethyl 7-oxo-7H-benzo[de]imidazo[5,1-a]iso-quinoline-11-carboxyl-ate-tri-fluoro-acetic acid (1/1).

The structure of the title tri-fluoro-acetic acid adduct, C17H12N2O3·C2HF3O2, contains a tri-fluoro-acetic acid mol-ecule hydrogen bonded to the imine N atom of the imidazole ring of a nearly planar four-fused-ring system (r.m.s. deviatiation = 0.013 Å). The carb-oxy-lic acid group of the triflouro-acetic acid mol-ecule is twisted with respect to the mean plane of the four-fused-ring sytem by 75.9 (2)°. A short intra-molecular C-H⋯O hydrogen bond occurs. In the crystal, the adduct mol-ecules are arranged into stacks along the b axis via π-π inter-actions between imidazole rings and between imidazole and one of the benzene rings [centroid-centroid distances 3.352 (2) and 3.485 (2) Å, respectively]. Molecules are linked via C-H⋯O hydrogen bonds, forming an alternating polymeric head-to-head/tail-to-tail stepped chain approximately along the a-axis direction and tilted on an axis bisecting the b and c axes.

rac-Dichlorido[3-eth-oxy-3-(1-ethyl-1H-benzimidazol-2-yl)-2,3-dihydro-1H-pyrrolo-[1,2-a]benzimidazole]-copper(II).

The title complex, [CuCl(2)(C(21)H(22)N(4)O)], contains a bis-(benzimidazole) unit with a chiral bridgehead C atom that forms part of a tetra-hydro-pyrrole ring fused to one of the benzimidazoles. The chelate angle is 90.45 (9)° and the dihedral angle between the essentially planar benzimidazole fragments is 26.68 (9)°. The Cu(II) coordination geometry lies approximately midway between tetra-hedral and square planar. Overall, each chiral mol-ecule contains six fused rings, and a racemic mixture is formed with symmetry-related enanti-omers. In the crystal, C-H⋯π and C-H⋯Cl inter-actions link mol-ecules into a supra-molecular chain along the a-axis direction.

A second monoclinic polymorph of {bis-[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borato}{tris-[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borato}cobalt(II): a structure containing a B-H⋯Co agostic inter-action.

The title compound, [Co(C(10)H(10)BF(6)N(4))(C(15)H(13)BF(9)N(6))], is a polymorph of the previously reported neutral cobalt(II) complex [Stibrany & Potenza (2010 ▶). Acta Cryst. E66, m506-m507], which contains one each of the monoanionic ligands, bis-[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borate (Bp) and tris-[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borate (Tp). A distorted octahedral coordination geometry of the Co(II) atom results from ligation of an H atom, which is part of an agostic B-H⋯Co inter-action [H⋯Co = 2.12 (3) Å], and by five imine N atoms, two from a Bp ligand and three from a Tp ligand. Weak intra- and inter-molecular C-F⋯π inter-actions with F⋯centroid distances ranging from 3.025 (4) to 3.605 (4) Šare observed.

{Bis[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borato}{tris-[5-methyl-3-(trifluoro-meth-yl)pyrazol-1-yl]borato}cobalt(II): a structure containing a B-H⋯Co agostic inter-action.

The title compound, [Co(C(10)H(10)BF(6)N(4))(C(15)H(13)BF(9)N(6))], is a neutral Co(II) complex which contains one each of the anionic ligands, bis-(3-trifluoro-methyl-5-methyl-pyrazol-1-yl)borate (Bp) and tris-(3-trifluoro-methyl-5-methyl-pyrazol-1-yl)borate (Tp). A distorted octa-hedral coordination geometry results from ligation of an H atom, which is part of an agostic B-H⋯Co inter-action (H⋯Co = 2.17 Å), and by five imine N atoms, two from a Bp ligand and three from a Tp ligand. In the crystal, mol-ecules form layers parallel to the (10) planes, and the layers are linked along the a axis by C-H⋯F hydrogen bonds. An intra-molecular C-H⋯F inter-action also occurs.

(E)-1,2-Bis(1-propyl-5,6-dimethyl-1H-benzimidazol-2-yl)ethene.

In the title compound, C(26)H(32)N(4), the essentially planar (r.m.s. deviations of 0.0053 and 0.0242 Å) benzimidazole fragments are trans with respect to a central ethene fragment, and are canted in opposite directions by 2.78 (6) and 5.87 (6)° with respect to the ethene plane, giving the mol-ecule a propeller conformation. The terminal ethyl fragments of the pendant n-propyl groups protrude to either side of the benzimidazole planes. Overall, the mol-ecule exhibits a pseudo-center of symmetry at the mid-point of the ethene fragment. Both π-π stacking and typical C-H⋯π inter-actions are notably absent, as are inter-molecular hydrogen bonds. When viewed along the a axis, the structure appears as criss-crossed layers of mol-ecules with the planar fragments separated along the c-cell direction by the protruding ethyl groups.

Dibromido[1,1'-dibutyl-2,2'-(pentane-1,1-di-yl)di-1H-benzimidazole]-copper(II).

In the title compound, [CuBr(2)(C(27)H(36)N(4))], the Cu(II) ion exhibits a distorted tetra-hedral coordination geometry provided by two bromide ions and by chelation of two imine N-atom donors from a bis-(benzimidazole) ligand. Chelation results in a six-membered boat-shaped ring which links the benzimidazole groups. Each bis-(benzimidazole) fragment contains three n-butyl substituents, two of which have the expected trans conformation; the third exhibits the higher-energy cis conformation, an orientation consistent with several short intra-molecular C-H⋯Br inter-actions. Essentially planar (r.m.s. deviations of 0.0101 and 0.0183 Å) benzimidazole groups are oriented so as to give the bis-(benzimidazole) fragment a V-shaped appearance in profile with the cis and trans n-butyl groups directed to opposite sides of the planes. In the crystal, columns of mol-ecules along the b-axis direction form layers parallel to the (202) planes. Within a given column, the mol-ecules are linked by C-H⋯Br hydrogen bonds. The mol-ecules in adjacent columns are also linked by inter-molecular C-H⋯π interactions, forming a three-dimensional network.

Structures of 1-hydrophenanthroimidazoles: building blocks in the synthesis of expanded-ring bis(imidazoles).

The structures of 1H-phenanthro[9,10-d]imidazole, C15H10N2, (I), and 3,6-dibromo-1H-phenanthro[9,10-d]imidazole hemihydrate, C15H8Br2N(2).0.5H2O, (II), contain hydrogen-bonded polymeric chains linked by columns of pi-pi stacked essentially planar phenanthroimidazole monomers. In the structure of (I), the asymmetric unit consists of two independent molecules, denoted (Ia) and (Ib), of 1H-phenanthro[9,10-d]imidazole. Alternating molecules of (Ia) and (Ib), canted by 79.07 (3) degrees, form hydrogen-bonded zigzag polymer chains along the a-cell direction. The chains are linked by pi-pi stacking of molecules of (Ia) and (Ib) along the b-cell direction. In the structure of (II), the asymmetric unit consists of two independent molecules of 3,6-dibromo-1H-phenanthro[9,10-d]imidazole, denoted (IIa) and (IIb), along with a molecule of water. Alternating molecules of (IIa), (IIb) and water form hydrogen-bonded polymer chains along the [110] direction. The donor-acceptor distances in these N(imine)...H-O(water)...H-N(amine) hydrogen bonds are the shortest thus far reported for imidazole amine and imine hydrogen-bond interactions with water. Centrosymmetrically related molecules of (IIa) and (IIb) alternate in columns along the a-cell direction and are canted by 48.27 (3) degrees. The present study provides the first examples of structurally characterized 1H-phenanthroimidazoles.

Solid-state changes in ligand-to-metal charge-transfer spectra of (NH3)5Ru(III)(2,4-dihydroxybenzoate) and (NH3)5Ru(III)(xanthine) chromophores.

Five distorted-octahedral complexes containing (NH3)5Ru(III)L ions, where L = 2,4-dihydroxybenzoate or a xanthine, have been studied using a combination of X-ray crystallography, solution and polarized single-crystal electronic absorption spectroscopy, and first principles electronic structure computational techniques. Both yellow (2) and red (3) forms of the complex (NH3)5Ru(III)L, where L = 2,4-dihydroxybenzoate, as well as three xanthine complexes in which L = hypoxanthine-kappaN(7) (4), 7-methylhypoxanthine-kappaN(9) (5), and 1,3,9-trimethylxanthine-kappaN(7) (6) were examined. In the solid state, some of these complexes exhibit split low-energy ligand-to-metal charge-transfer (LMCT) bands. Traditional solid-state effects, such as ligand pi-pi overlap or hydrogen bonding that might lead to splitting of electronic absorption bands, were probed in an attempt to identify the origins of these unusual observations. For comparison, companion studies were carried out for spectroscopically normal reference complexes of the same ligands. Time-dependent density-functional theory (TD-DFT) calculations, employing modified B3LYP-type functionals with increased contributions of exact exchange, attribute the color change in the crystalline complexes 2 and 3 to pi(ligand) --> Ru[d(pi)] LMCT bands which, in the red form (3), arise from ligand donor pi-orbitals split by strongly overlapping phenyl moieties in centrosymmetric (NH3)5Ru(III)(2,4-dihydroxybenzoate) dimers. Complex 5 does not show split visible absorptions, whereas both the polarizations and energies of the split visible absorptions shown by 4 and 6 also suggest assignment as LMCT. No support is found for relating the split absorptions of 4 and 6 to the details of pi-pi xanthine overlap in the solid state; indeed, complex 4 enjoys considerably less pi-stacking overlap than does 5. We feel compelled to attribute the split absorptions in crystalline 4 and 6 to the emergence of a LMCT transition originating in the carbonyl lone pair, potentially deriving intensity from the significant intramolecular N-H...O hydrogen bonding present in both 4 and 6 (but not in 5). The electronic structure calculations suggest an O(n) --> Ru[d(sigma*)] LMCT transition; however, this novel assignment must be considered tentative.

An alternating copolymer containing trigonal planar homocoordinated copper(I) ions: catena-poly[[[bis[mu-(E)-1,2-bis(1-ethyl-1H-benzimidazol-2-yl)ethene-kappa2N3:N3']dicopper(I)]-mu-(E)-1,2-bis(1-ethyl-1H-benzimidazol-2-yl)ethene-kappa2N3:N3'] bis(perchlorate) acetonitrile disolvate].

The structure of the title salt, {[Cu(2)(C(20)H(20)N(4))(3)](ClO(4))(2) x 2 CH(3)CN}(n), consists of linear [Cu(I)(2)L(3)] polymer chains [L is (E)-1,2-bis(1-ethyl-1H-benzimidazol-2-yl)ethene], which extend along the c cell direction, interspersed with disordered perchlorate ions and acetonitrile solvent molecules. In a given chain, each Cu(I) ion exhibits distorted trigonal planar coordination to three L ligands; two of these are linked to adjacent Cu(I) ions to form dimeric units containing 14-membered rings that adopt a twisted-loop configuration, stabilized by pi-pi interactions between the ethene fragments of the two ligands. The dimeric units exhibit diad symmetry (twofold axis sites in I2/a) and are linked by a third, centrosymmetric, S-shaped L ligand (inversion centers in I2/a) to form the copolymer chain. When viewed along the b cell direction, the 14-membered rings appear as vacant ellipses that form channels parallel to the b axis. The walls of the channels are formed by the benzimidazole fragments of the dimeric units. This study of a novel alternating copolymer containing homocoordinated Cu(I) ions demonstrates further the usefulness of bis(benzimidazoles) as versatile bidentate ligands.

A tris(pyrazolyl) eta6-arene ligand that selects Cu(I) over Cu(II).

1,3,5-Tris{2'-[(pyrazol-1-yl)methyl]phenyl}benzene, 4, and its complexes with Cu(I) and Ag(I) have been prepared and characterized. Both CuI4 and AgI4 triflate crystallize in the rhombohedral space group R3, with the cations and anions each exhibiting crystallographically imposed 3-fold (C3) symmetry. In both complexes, 4 behaves as a tris(pyrazolyl) eta6-arene ligand whose arms act as three-pronged tweezers to form chiral, propeller-like cations with pyramidal MN(pyrazole)3 coordination geometries. Centers of symmetry in the space group ensure that the crystals are racemates, with equal numbers of P,P,P and M,M,M enantiomers. In broad outline, each cation is shaped like a three-legged stool, with the metal ion centered at the top and pointed downward from a triangular N(pyrazole) plane toward the center of gravity (Cg) of the central benzene ring (a metal-endo conformation), which constitutes the bottom shelf of the stool. The Cu(I)...Cg and Ag(I)...Cg distances, 3.195(2) and 3.165(2) A, respectively, support the existence of an eta6 bonding interaction with Ag(I) and, to a lesser extent, with Cu(I). NMR data for AgI4 suggest rapid interconversion of this cation in solution between P,P,P and M,M,M enantiomers. Our inability to prepare any Cu(II) complexes with 4 is consistent with cyclovoltammetric results, which suggest that the ligand is more easily oxidized than Cu(I).

Structural and spectroscopic features of mono- and binuclear nickel(II) complexes with tetradentate N(amine)2S(thiolate)2 ligation.

Three complexes containing Ni(II)N(amine)2S(thiolate)2 units have been prepared and characterized. Both (R,R)-N,N'-bis(1-carboxy-2-mercaptoethyl)-1,2-diaminoethane [(R,R)-1] and N,N'-bis(2-methyl-2-mercaptoprop-1-yl)-1,3-diamino-2,2-dimethylpropane (4) act as tetradentate S-N-N-S ligands to form complexes Ni((R,R)-1) and Ni4 with nearly planar cis-NiN2S2 units. The N-Ni-N and S-Ni-S angles differ significantly in the two complexes yet are very nearly supplementary. The 1,3-disubstituted cyclohexane species rac-N,N'-bis(2-mercapto-2-methylprop-1-yl)-1,3-cyclohexanediamine (6) behaves as a bis(bidentate-N,S) ligand to form an unexpectedly intense-blue dinickel complex (1S,3R,1'S,3'R)-7, which contains two trans-NiN2S2 units bridged by 1,3-disubstituted cyclohexane groups. The coordination geometry in (1S,3R,1'S,3'R)-7 is distorted 15 degrees toward tetrahedral, most likely as a result of steric crowding, suggested by several short contacts between the NiS2 units and both the cyclohexyl and gem-dimethyl groups of the N,S-chelate rings. The complexes exhibit rich UV-vis spectra, whose deconvoluted bands are now fully assigned, from low to high energy, as ligand field (LF), pi(S) --> Ni(II) ligand-to-metal charge transfer (LMCT), sigma(S) --> Ni(II) LMCT, sigma(N) --> Ni(II) LMCT, localized S, and S,N Rydberg transitions. The unusually intense LF absorptions shown by (1S,3R,1'S,3'R)-7 are thought to result from relaxation of the Laporte restriction arising from the 15 degrees tetrahedral twist.

Three structures containing (E)-1,2-bis(benzimidazol-2-yl)ethene groups.

Two of the title compounds, namely (E)-1,2-bis(1-methylbenzimidazol-2-yl)ethene, C18H16N4, (Ib), and (E)-1,2-bis(1-ethylbenzimidazol-2-yl)ethene, C20H20N4, (Ic), consist of centrosymmetric trans-bis(1-alkylbenzimidazol-2-yl)ethene molecules, while 3-ethyl-2-[(E)-2-(1-ethylbenzimidazol-2-yl)ethenyl]benzimidazol-1-ium perchlorate, C20H21N4+.ClO4-, (II), contains the monoprotonated analogue of compound (Ic). In the three structures, the benzimidazole and benzimidazolium moieties are essentially planar; the geometric parameters for the ethene linkages and their bonds to the aromatic groups are consistent with double and single bonds, respectively, implying little, if any, conjugation of the central C=C bonds with the nitrogen-containing rings. The C-N bond lengths in the N=C-N part of the benzimidazole groups differ and are consistent with localized imine C=N and amine C-N linkages in (Ib) and (Ic); in contrast, the corresponding distances in the benzimidazolium cation are equal in (II), consistent with electron delocalization resulting from protonation of the amine N atom. Crystals of (Ib) and (Ic) contain columns of parallel molecules, which are linked by edge-over-edge C-H...pi overlap. The columns are linked to one another by C-H...pi interactions and, in the case of (Ib), C-H...N hydrogen bonds. Crystals of (II) contain layers of monocations linked by pi-pi interactions and separated by both perchlorate anions and the protruding ethyl groups; the cations and anions are linked by N-H...O hydrogen bonds.

A geometrically constraining bis(benzimidazole) ligand and its nearly tetrahedral complexes with Fe(II) and Mn(II).

2,2'-Bis[2-(1-propylbenzimidazol-2-yl)]biphenyl), 4, and its bis complexes with Fe(II) and Mn(II) have been prepared and characterized structurally and spectroscopically. Ligand 4 adopts an open, "trans" conformation in the solid state with the benzimidazole (BzIm) groups on opposite sides of the biphenyl unit. In its complexes with metal ions, a "cis" conformation is observed, and 4 behaves as a geometrically constraining bidentate ligand with four planar groups connected by three "hinges". Reaction of 4 with Fe(II) or Mn(II) yielded isomorphous crystals (space group Pnn2) of Fe(II)(4)2.(ClO4)2 and Mn(II)(4)2.(ClO4)2, in which the M(II)(4)2 cations exhibit distorted-tetrahedral coordination geometries (N-M-N angles, 109 +/- 11 degrees ) enforced by rigid, chiral nine-membered M(4) rings in the twist-boat-boat conformation. Individually, the cations show R,R or S,S stereochemistry, and the crystals are racemates. Mn(II)(4)2.(ClO4)2 exhibits a quasi-reversible Mn(II) --> Mn(III) oxidation at E(1/2) = 0.64 V; the corresponding Fe(II) --> Fe(III) oxidation occurs at E(1/2) = 1.76 V. The electrochemical stability of the Fe(III) oxidation state in this system suggests the possibility of isolating an unusual pseudotetrahedral Fe(III)N(BzIm)(4) species. Ultraviolet spectra of the iron and manganese complexes are dominated by absorptions of the ligand 4 blue-shifted by approximately 2000-3000 cm(-1). Ligand-field absorptions were observed for the Fe(II) complex; those for the Mn(II) complex were obscured by tailing ultraviolet absorptions. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-spin Mn(II) complex, while for the Fe(II) complex, the falloff of the magnetic moment with decreasing temperature is indicative of zero-field splitting with D approximately 4 cm(-1).

Charge-transfer spectra of structurally characterized mixed-valence thiolate-bridged Cu(I)/Cu(II) cluster complexes.

A series of Cu(II) and Cu(I)/Cu(II) complexes containing the cis-N(amine)(2)S(thiolate)(2) copper complex rac-2 has been synthesized to provide a basis for understanding the charge-transfer spectra of mixed-valence thiolate-bridged Cu(I)/Cu(II) complexes. In combination with Cu(Me(2)-13-N(4)ane), rac-2 yields a monobridged dinuclear homovalent adduct, rac-5, while reaction with CuCl yields the mixed-valance pentanuclear complex rac-6. In the presence of Cu(II)(acac)(2), chiral R,R-1 reacts to form a mixed-valence pentanuclear cation R,R-7. rac-6 exhibits a relatively short Cu(I). Cu(II) contact [2.8231(9) A] and associated structural features that suggest the presence of a weak Cu(I).Cu(II) interaction in a valence-trapped system. Additional structural features in rac-6 and R,R-7 include singly and doubly bridging thiolates, three- and four-coordinated Cu(I) ions, and varying Cu(I) ligand sets. These features extend the types and complexities of electronic absorptions significantly. Spectra of rac-6 and R,R-7 exhibit multiple overlapping absorptions over the entire visible and ultraviolet spectral regions studied, consonant with these observations. Trends resulting from variations in structure type and oxidation state permit a first approach toward developing a detailed assignment of the individual ligand Rydberg, LF, LMCT, MLCT, and possible MMCT absorptions in these complexes.

Aqueous vapor extraction: a previously unrecognized weathering process affecting oil spills in vigorously aerated water.

Simple evaporation of spilled oil is usually thought to be restricted to the smaller hydrocarbons (<15 carbons). We show that aeration of oil in water, at 22 degrees C, substantially extends this evaporation, leading to the loss of alkanes up to at least hexatricosane (nC36) and of polycyclic aromatic hydrocarbons with at least four rings (e.g., chrysene and its alkylated forms). This phenomenon is apparently related to steam distillation and should be considered as an important candidate pathway to explain the observed weathering of oil spilled from the OSSA II pipeline into the Río Desaguadero on the Bolivian Altiplano (approximately 3700 m), which occurred during a very turbulent flood.